Carton sealing apparatus



March 29, 1960 w. JONES CARTON SEALING APPARATUS 4 Sheets-Sheet 1 IN VENTOR.

A TTOENEYS.

Filed April 3, 1956 8 MMMN uo MI. 2 Q. AN AN M m S a z. 8 AA 5 n n o Vbo 0 50 V9 8 3 nimm 2/, s2 H 5 5 5 2 6. a. M on N v o w a. i Am M Illv Jw No on S M #9 3 map ma om m March 29, 1960 w JONES 2,930,175

CARTON SEALING APPARATUS 4 Sheets-Sheet 3 Filed April 3, 1956 BYImam/101m min-am ATTDEAM'YQ March 29, 1960 w, JONES 7 2,930,175

' CARTON SEALING APPARATUS Filed April 3, 1956 4 Sheets-Sheet 4 8wINVENTOR. fi mlwfiw nrragmy s,

CARTON SEALING APPARATUS Wicklii're Jones, Cincinnati, Ohio, assignor toR. A. Jones and Company, Inc., Covington, Ky., a corporation of KentuckyApplication April 3, 1956, Serial No. 575,741

2 Claims. (Cl. 53-388) This invention is directed to an apparatus andmethod for drying and sealing the adhesively coated flaps or cartons asthey issue from a cartoning machine with the flaps freshly glued andfolded to closed position. The apparatus is intended particularly forflaps having an adhesive coating which sets or dries rapidly whenheated, such as vegetable or animal glue applied in liquid form to theflaps.

One of the primary objects of the invention has been to utilizecontinuously advancing heat exchange elements which engage the freshlyglued flaps to hold them firmly in closed position while transferringheat to the flaps to dry the glue coating as the cartons advance throughthe apparatus to its discharge end.

In the disclosure which is selected to illustrate this principle, theopposite ends of the carton include inner and outer flaps, the liquidadhesive being applied by the cartoning machine to the outer flaps whilethey are in unfolded position. The machine then folds the glued outerflaps over upon the inner flaps with the adhesive coating of the outerflaps in facial contact with the previously folded inner flaps. Thecarton is then advanced in this condition from the discharge end of thecartoning machine to the present apparatus for final drying and seal-1ng.

In order to dry and seal the flaps at both ends concurrently, thesealing apparatus embodies a pair of parallel conveyor runs whichadvance continuouslyin unison and carry the heat exchange elements, thecartons.

being engaged endwisely between the two conveyor runs. The receiving endof the conveyor runs arecontiguous to the discharge end of the cartoningmachine, such that the folded and glued flaps are immediately engaged bythe heating elements under sufiicient pressure to hold them firmlyclosed and to advance them by frictional engagement while the elementstransfer heat to the flaps. carried out as the cartons are advancedbetween the heating elements and reach the discharge end of the conveyorruns permanently dried and sealed.

The heat exchange elements preferably consist of flat the ends of thecartons. The heat stored in the slats metal bars having a mass to absorbsuflicient heat energy to dry the glue by heat transfer while engagingis transmitted by direct conduction to the flaps and From the foregoing,it will be recognized that one of the features of the invention consistsin taking advantage of the natural heat absorbing and transferringaction of the metal slats to apply maximum heat to the freshly gluedflaps when the moisture content is greatest, the slat temperaturegradually decreasing as heat The drying process is thereforeprogressively v 2,930,175 i-PatentedMar. .29, 1960 is exchanged duringthe drying process. Thisaction drives off the moisture as rapidly aspossible while at the same time avoiding excessive heat which may leadto deterioration ing.

The invention further takes advantage of the heat exchange principle toprovide an exceptionally simple mechanism. In other words, the heatexchange slats allow the use of stationary heating elements, such thatthe heat is absorbed and stored by the moving slats, then transmitted tothe flaps. This avoids mounting the heatingelements themselves on theconveyor runs with the attendant apparatus to conduct the heat to themas they advance.

In the structure which illustrates the practical appli-' cation of theseprinciples, two self-contained heat transfer conveyors are mountedparallel with one another, each conveyor including an endless conveyorchain carrying metal heat exchange slats which advance along opposedcarton-scaling runs and return runs. Each conveyor includes a stationaryheating section extending along the return run to heat the returningslats. The parallel conveyor chains advance at uniform speeds aroundidler sprocketsat the receiving end and thus delineate a convergingcarton receiving throat leading to the carton-. The cartons are advancedinto the con-' tuation of the adjustment mechanism changes the spacingof the opposed slats along the carton-sealing runs.

According to the present disclosure, the sealing apparatus is drivenindependently of the cartoning machine by its own variable speed drivingmechanism which advances both conveyor chains at a uniform rate. The

variable speed mechanism'allows the rate of conveyor advancement to beregulated to conform to the output- Moreover, should the carofthecartoning machine. toning machine stop for any reason, the sealingapparatus continues operating so'as to unload itself. This pre ventsbuild-up of excessive heat with attendant damage to the cartons and alsoprevents overheating of the heat;

exchange elements. The transverse adjustment and the speed regulationmakes it possible to adapt the apparatus practically to any operatingcondition which may be encountered.

The present apparatus is intended for use inconjunction with the highspeed article feeding apparatus disclosed in my co-pending application,Serial No. 576,096, filed on April 4, 6, now'PatentNo. 2,805,755. The

feeding apparatus disclosed in the patent advances the articles in groupformation to the intake end of a car-- toning machine which inserts thegroups of articles into I cartons, applies adhesive .to thecarton'fiaps, then folds the flaps one upon the other. At its dischargeend, the cartoningmechanism advances the cartons betweenbelt runs withthe freshly glued flaps held in closed position for'transfer to thereceiving end of the present drying I .and sealing apparatus. Althoughthe invention is disclo'sed in relation "to a. carton having overlappingglued 'fiaps at opposite ends,;. it will be understood that the sealingprinciples are in, tended to. be applied to various other types ofcartons "and to various types of heat sensitive adhesive. l

of the. paper board flaps or adhesive coat- 3 The various features ofthe invention will be more fully understood by those skilled in the artfrom the fol.- lowing detailed disclosure in conjunction with theattached drawings. In the drawings: i

Figures '1-and 2 illustrate the'flap sealing apparatus as viewedfrom theside, Figure-1" representing the receiving portion'and Figure 2representingthedischarge portion of the apparatus. The full length sideview has been divided lengthwise and placed one above the other=tobetter illustrate the mechanism.

Figures 3 and 4 illustrate the apparatus in plan view, the'two sectionslikewise being-placed one above the other.

Figure 5 is an enlarged cross section taken along line 55. of Figure 1..5

Figure 6 is a sectional view taken along line 6.-6 of Figure 2,illustrating the variable speed driving-system of the een eyor chains. va

figu e-7 is a perspective view of a carton with the flaps open andadhesive applied, ready for folding.

- Figure 8 is .a perspective view showing :the carton in closed positionas it issues from the cartoning machine and enters the receiving end ofthe sealing apparatus.

General arrangement Referring to Figures 3 and 4, the drying apparatuscomprises a pair of longitudinal heat transfer conveyor assemblies,indicated generally at 1 and 2, which extend parallel with one anotherand delineate the longitudinal carton way indicated at 3. Each heattransfer conveyor is a self-contained unit and includes acontinuously"advancing, endless chain loop 4 carrying closely spacedvertical heat exchange slats 5 which engage the cartons-6 endwiselyalong the way 3 and apply heat and controlled pressure to the freshlyglued and folded end flaps. The carton-engaging conveyor runs 7, alongthe carton way 3, advance at uniform speed in the direction indicated bythe arrow from the receiving end 8 to the discharge end 10 of theapparatus. The chains of both conveyors are driven from a variable speeddriving unit 11, as explained later in detail.

As the chain runs advance, they carry the heat exchange cleats or slats5 around the driving sprockets 12 "at the discharge end, thusdisengaging the sealed cartons. Thereafter, the slats are advancedalongthe return runs 13 where they are presented to the stationaryheating' elements 14 in the direction indicated by the arrows, thusprogressively raising the temperature of the slatsas they approach thereceiving end 8. At this point, the heated slats pass around the idlersprockets 15 and thus delineate the converging receiving end 8 whichengages progressively the opposite end flaps as the closed carton issuesfrom the cartoning machine.

It will be observed that the temperature of the slats is at maximum whenthey engage the cartons at the receiving end so as to drive off themoisture from the adhesive most rapidly while the moisture content isgreatest. Thereafter, as the heat stored in the slats is absorbed intothe glued flaps, the slat' temperature progressively decreases.Accordingly, the drying temperature may be relatively high to carry outthe treatment in the shortest possible time, while at the same time,avoidingdamage to the flaps orto the adhesive due to overheating. Therate of advancement of the heat exchange slats, combined with the lengthof the conveyor apparatus, provides a drying period of sufficientduration to dry and seal the flaps completely before the cartons reachthedischarge end.

According to the present example, electrical heating elements 14 areutilizedto heat the slats. These elements extend lengthwise forapproirimat'ely half the length of theapparatus, as shown in Figures 3and 4, and provide sufficient heat for efficient operation. The heatingelements are mounted instationar'y position and have flat 4 facescontiguous to the fiat faces of the returning slats as shown in Figure5.-

The lineal advancement of the two chain loops 4 is made to correspond tothe output of the cartoning machine by regulation of the power unit 11.The slats along the way 3 engage the glued flaps under sufiicientpressure to hold them firmly in closed position and to advance thecartons by frictional engagement while the weight load of the cartons iscarried by the longitudinal support rails 16. In order to accommodatecartons having different lengths and also to regulate the pressure ofthe slats against the carton, the two self-contained heat transferconveyor units 1 and 2 are shiftable transversely relative to oneanother. In the present embodiment, the conveyor 1 is permanentlyattached to the frame26, while the conveyor 2 is shiftable transverselyupon the frame by a hand-operated adjustment mechanism which isindicated generally at 17, operated by a crank 18. This mechanismincludes a series of threaded shafts journalled'in the frame andextending crosswise in threaded engagement with the shiftable conveyor 2at a series of points spaced along its length. The adjustment crank 18is in driving connection with all of the threaded cross shafts so as toshift the conveyor 2 uniformly along its full length. As explained laterin detail, all components of the adjustable conveyor 2 are mounted uponshiftable brackets slidably carried upon cross members of the frame andin threaded connection with-the cross adjustment shafts.

--Referring to Figure 3, the cartons 6 are delivered from the cartoningmachine by the parallel belt runs 20. The ends of the belt runs 20 passaround rollers 21 located adjacent the idler sprockets 15, such that thecartons are transferred with their freshly glued flaps held in foldedposition. It will be understood that the delivery apparatus will varyaccording to the design of the cartoner and that the sealing'apparatusmay be adapted to any machine which delivers the carton in thiscondition.

Referring to Figure 7, which illustrates the type of 'carton for whichthe machine is intended, the carton 6 is formed of the usual paperboardmaterial and includes upper and lower flaps 22 and a pair of inner fiaps23. This carton is extensively used in packaging canned beer and is ofthe twelve-can size. The cartoning mechanism, as disclosed in theco-pending applications, is arranged by suitable adjustment to handleeither the twelve-can carton or the shorter six-can carton. Theadjustment mechanism 17 accommodates the sealing mechanism to bothcarton sizes as described later in detail.

During passage of the carton through the cartoning mechanism, the groupof cans is shifted endwisely into the carton, then the inner flaps 23are folded to the closed position shown in Figure 7. The upper and lowerflaps 22 remain in the vertical position during passage through a gluingstation which applies the coating of wet glue 24 to the flaps.Thereafter, the glued flaps are folded over upon the inner flaps 23 asshow in Figure 8, then the carton is discharged into the dryingapparatus.

The liquid glue or adhesive coating 24 may be of any conventional typebest suited to the composition of the paper-board material of thecarton, for example, a waterbase vegetable glue. It may also consist ofa synthetic adhesive material of a type which satisfies the operatingconditions of the drying apparatus.

The chain runs of the drying apparatus advance at a lineal ratecorresponding to the output of the cartoning machine, for example, 120cartons per minute. Accord ing to the present example, the heat exchangeslats 5 are heated to a temperature between 250 and 300 degrees F. atthe receiving end. The temperature is controlled 'by a thermostat (notshown) which maintains heating elements 14 at the desired temperatureconstantly. The most etficient drying'temperature depends on the cartonmaterial and composition of the adhesive and is obtained by regulatingthe thermostat to obtain the bestresults under operating conditions.Under normal operating conditions, each carton is advanced throughthefdrying' apparatus rapidly, for example in 20 seconds or less and isdischarged ready for shipment or sale.

Structural details To prevent interference between the slats and cartonsas the slats pass around the sprockets at the intake throat, the leadingedges of the slats, as indicated at 5a in Figure 3, may be beveled orcurved to conform generally to the of the machine by a cross member 25in the form of a channel, the ends of the angle irons being connected tothe channel by brackets 28. Channel 25 represents the end framing memberof the cartoning machine to which the drying apparatus is intended. Theframe further includes a series of intermediate cross bars 30 spacedapart from one another along the frame and attached permanently to theangle irons. A support post 31 braces the frame at a point intermediateits length.

At the discharge end of the dryer, there is provided a cross plate 32having a cross groove for mounting the bearing brackets 33-33 of thedrive sprockets 12. Each driving sprocket is keyed to a vertical shaft34 and these shafts in turn are driven in unison by the variable speedunit 11.

The driving system of the chain runs is best shown in Figure 6. Themotor 35 of unit 11 is mounted upon a sliding base 36 and is shifted bya hand wheel 37 relative to the variable sheave 38 to obtain the desiredconveyor speed. The motor sheave (not shown) is connected by a belt 40to sheave 38; this arrangement is conventional and well understood inthe art. The sheave 38 is mounted upon a worm shaft 41 journalled in awormtbox 42 attached to the cross plate 32. The shaft 41 includes a worm43 meshing with a worm wheel 44 keyed to a cross shaft 45. Shaft 45 hasits opposite ends journalled in bearings 46 projecting downwardly fromthe bearing brackets 33. Each vertical sprocket shaft 34 includes abevel gear 47 meshing with a respective bevel gear 48 of cross shaft 45;therefore, shaft 45 rotates the driving sprockets in opposite directionsas indicated by the arrows in Figure 4, so as to advance the innercartonengaging runs 7 at uniform speed in the same direction. Adjustmentof hand wheel 37 thus varies the speed of both conveyor sprockets andpermits the conveyor speed to be regulated to suit the operating speedof the cartoning machine.

The idler sprockets 15 at the rceiving end of the conveyor are mountedon stub shafts 50 journalled in bearing brackets 51. The bearingbrackets are slidably engaged in a cross groove formed in the crossplate 52, at thereceiving end. This is similar to that described withreference to the driving sprockets 12.

As noted earlier, the self-contained heat exchange conveyor 2 isadjustable laterally with respect to the conveyor unit 1. For thispurpose, all components of conveyor 2 are carried upon intermediateslide brackets 53 carried on the intermediate cross bars 30. As shown inFigure 5, the adjustable conveyor 2 is shiftable from the position shownin full lines (twelve-can carton) to the position shown by the brokenline 54, which represents the end of the six-can carton. Upon makingthis adjustment, the slide brackets 53 of conveyor 2 are shiftedinwardly along their cross bars 30 and the bearing brackets 33 and 51are shifted along their cross plates 32 and 52.

The conveyor units l and 2 are in duplicate, both being carried byduplicate slide brackets and bearing brackets attached rigidly to thecross members. Referring to-Figure'fi, each slide bracket 53 comprises abase plate: 55 having an .inner lug 56 supporting the longitudinal slidebar 16, a second lug 57 supporting the inner chain run 7, and an outerlug'58 supporting the return chain run 13. The three'lugs are connectedtogether by a web 60. The second lug 57 of each bracket is joined to achain support plate 61 extending for the full length of each chain run.Plate 61 includes a tracking rail 62 along its upper edge having .agroove engaging the flange 63 of a series of support rollers 64journalled upon the upper end of the heat exchange slats 5. As shown inFigure 3, the chain runs include a sufficient number of support rollers64 to sustain the runs without imposing vertical pressure, upon thechain links. The chain links are conventional and track against abacking rail 65 alsosecured to the'plate 61.. As shown,

each chain link is provided with a heating slat,the links havingbrackets 66 secured to the slats. The outward thrust of the slats iscarried by the bearing strips 67-67, the upper strip being attached tothe tracking rail 62 and the lower strip being attached to a rail 68.The several rails extend for the full length of the conveyor as shown inFigures 3 and 4, suchthat the pressure of the heating slats istransmitted to the brackets 53 outwardly, the bearing strips providing asmooth sliding surface for the slats. 1

It will be noted at this point, that the, base of each intermediateslide bracket53 of conveyor 2 is secured by screws 70 threaded into thecross bar 30. To providev transverse adjustment, each base plate 55 ofthe bracket includes slots 71 traversed by the, screws. These bolts areloosened when it is necessary to adjust the conveyor 2.

Each intermediate bracket .53 of conveyor 2 further includes adownwardly depending lug 72 which is traversed by a screw shaft 73 ofthe adjustment mechanism, so as to shift the bracket laterally when thescrew is rotated (Figure 5). As best shown in Figures 1 and 2, theseveral screw shafts are rotated in. unison by respective pairs ofsprockets 74, each adjacent pair of sprockets being connected by chainloops 75 for rotating the shafts in the same direction.

As shown in Figure 5, each adjustment shaft has its ment crank 18. Asviewed in Figure 1, the chain loops 75 extend from the two sprockets ofthe crank shaftand transmit the drive to the two shafts on oppositesides of the crank driven shaft; from the two adjoining shafts, the Idrive is carried by similar chain loops to the adjustment.

shafts of the remaining brackets. This mechanism shifts all of the slidebrackets uniformly in the same direction upon operation of the crank.

The longitudinal slide rails 16, as noted earlier, are

attached in common to all of the slide brackets; hence, the rail 16 andslide brackets shift as a unit when the.

adjustment mechanism is actuated. Referring to Figures 3 and 4, it willbe. noted that the longitudinal rails 16 project outwardly to. thebearing brackets 33 at the: discharge end and to thebearin'g brackets 51at the receiv- 'ing end. As shown in-Figure 6, the bearing brackets 33at the discharge end' include lugs 81 attached to the endwise extensionsof the longitudinal slide rails 15. The

bearing brackets 51 atthe receivingend.include-similar The adjustment'shafts of the several slide brackets are identical except that theshaft shown in Figure 5 has an endwise extension to receive the adjust-.

'7 lugs 81 connected to the end of the rails 16; therefore, theadjustment motion of conveyor 2 is carried to its slid ablebearin'g'brackets by the longitudinal slide rail 16.

It will benote'd'in' Figure 6, that the'shiftable bearing bracket 33 of.conveyor.2 'isheld in position by' holddown screws 82 similar to thescrews 70 of the'slide brackets 53; In a similar manner, thebracketincludes slots 83, the screws passing through the slots and threadedinto the cross plate 32, permitting transverse shifting of the bearingbrackets when the screws are loosened. Slide bearing bracket 33 furtherincludes a tongue 84 engaged in the cross groove 85 of its cross plate32; The keyed connection prevents longitudinal displacement of thebearing bracket under chain tension when the screws 82 are loosened andalso guides the bearing bracket smoothly as it is shifted. i

Referring again to Figure 6, it will be noted that the downwardlydepending boss 86 of the slidable bearing bracket passes through a crossslot 87 in its cross plate 32 to permit transverse shifting; To permitthe bevel gear 48 of cross shaft 45 to shift with the bearing bracket,the bevel gear slidably engages an elongated key 88 fixed in the endportion of the cross shaft. The bevel gear remains in mesh with itscompanion bevel gear 47 and remains keyed to the cross shaft uponadjustment.

The adjustable bearing bracket 51 at the receiving end is slidablymounted upon its cross plate 52 in substantially the same manner,including the hold-down screws 32 which are loosened to permitadjustment. The bracket also includes a tongue 84 slidably keyed in thegroove 85 of its cross plate. Since the arrangement is substantially thesame as that of the discharge end, the structure has not beenillustrated in detail.

The transverse adjustment range of the slidable brackets and bearings ofconveyor unit 2 is sufiicient to bring the heat exchange slats to theplane of the broken line 54 (Figure which represents the end of asix-can carton, as noted earlier. It will also be recognized that theadjustment mechanism permits precise regulation of the pressure appliedagainst the opposite ends of the cartons in order to obtain the bestoperating conditions.

As pointed out earlier, the components of the fixed conveyor unit 1 aresimilar to those of conveyor'units 2. Since the unit is fixed, theseveral slots are omitted and the brackets are attached rigidly byscrews '70 and 82 threaded into the cross members of the brackets, theadjustment shafts 73 and lugs 72 being omitted.

The return run 13 of each conveyor loop is supported upon tracking rail90 engaging the rollers 64 and having a groove engaging theflange .63 asdescribed with reference to the carton-engaging run 7. Rail 90 is rightangular in cross section and its lower portion includes a backing rail91 engaging the rollers of the chain links. This structure guides thereturning chain runs and slats in a plane contiguous to the flat facesof the heating elements 14.

As shown in Figures 1 and 3, the two conveyor assemblies each include aslack control sprocket 92 which is spring urged outwardly to maintainthe chain loop in taut condition. Sincethe chain loops expand lengthwiseas they are heated 'to operating temperature, the spring loadedsprockets take up the slackwhich would otherwise prevail. Described indetail, each sprocket is journalled upon astub shaft 93 mounted in theswinging end of a tension arm 94. The opposite end-of each tension armis pivoted upon a shaft 95 attached to a bar 96 projecting outwardlyfrom the longitudinal slide rail 16. The lower end of shaft 95 has acounter-turned screw threaded portion passing through the bar andengaged by a nut 97, locking the shaft against rotation in thebar andleaving the tensio'n'arin94'free" to pivot. The shaft projects upwardlyand carries a torsion spring 98 having its upper and anchored to acollar 100 pinned to the shaft. The torsion springs are preloadedto urgethe tension arms outwardly 'under the required pressure.

Since the mounting bars 96 are attached to the slide rails 16, thesprocket assembly of the shiftable conveyor 2 moves with the conveyorwhen an adjustment is made.

According to the present example shown in Figure 5, each chain run isheated by two parallel rows of heating elements 14 mounted in a commonvertical plane in end-to-end relationship." 'Each element is carried bypairs of spacer rods 101 projecting from opposite ends of the elements.The spacer rods are secured to respective angle brackets 102 attached tothe mounting bracket 53, the angle brackets being in the form of rightangular plates as viewed in Figure 5, thereby partially surrounding thereturn chain runs and heating elements. The ends of the angle bracketsare attached to the base and outer lug of the mounting brackets 53, thussupporting the heating elements firmly in position. Electrical energy issupplied to the heating elements by the usual cable system having heatregulating thermostats (not shown) interposed in the circuit for heatcontrol. Since the heating elements are carried directly upon the slidebrackets 53, the components all shift without interference uponadjustment of conveyor unit 2.

As viewed in Figure 5, two rows of heating elements provide a heatingarea extending for the full length of the heat exchange slats 5, eachelement having a flat face 103 presented to the surface of the slats.The fiat faces of the heating elements are located contiguous to thefiat heat exchange slats and the tracking rails guide the returningslats accurately along the heating plane;

ltwill be noted that the flat faces of the heating elements and slatshave an area substantially equal to the endwise area of the cartons,such that the entire fiap area is heated uniformly during the dryingprocess. In the present example, the slats are formed of stainless steelto inhibit oxidation and preserve the efficiency of the apparatus.

As indicated in broken lines (Figure 5), the heat exchange conveyors 2preferably are provided with guards 34 partially surrounding the heatingelements to protect the operator. The guards 104 are generally rightangular in cross section corresponding to the cross section of the anglebrackets 102 and extend for the full length of the apparatus. The innersurface of the guards includes a liner of heat insulating material, suchas asbestos, to prevent the exposed guards from becoming hot. The guardsfurther conserve heat since they partially enclose the heating elementsand shield them from air currents.

Having described my invention, I claim:

1. An apparatus for sealing a carton having closure flaps which formopposed walls thereof, said flaps overlapping one another in closedposition and having heat sealing adhesive therebetween, said apparatuscomprising a frame, a' pair of self-contained longitudinal heat transferconveyor units shiftably mounted in a substantially horizontal plane andin parallel relationship upon said frame, adjustment means connected toat least one of said conveyor units for shifting the same transverselyupon said frame relative to one another, each of said conveyor unitshaving an endless conveyor chain including a series of heat exchangeelements residing in a sub stantially vertical plane, said endlessconveyor chains having opposed carton-engaging runs and respectivereturn runs, said adjustment means locating said opposed heat exchangeelements along said carton-engaging runs at a spacing to embrace theopposed closure flaps of the carton, said heat exchange elements holdingsaid flaps in closed position, driving means connected to said conveyorchains for advancing the heat exchange elements inthe same directionalong the carton-engaging runs, thereby advancing the carton along saidruns, respective heating means mounted upon said conveyor units alongsaid return runs adjacent the heat exchange elements, said heating meansresiding adjacent the heat exchange elements on the side opposite theconveyor chain thereof, said heating means transmitting heat to saidelements and conveyor chains during advancement along said return runsfor transfer to said closure flaps during advancement of the cartonalong the cartonengaging runs, said heating means shifting transverselyin unison with the conveyor unit upon adjustment thereof by saidadjustment means, a respective slack control element mounted on each ofsaid self-contained conveyor units and engaging the endless conveyorchain thereof, and resilient means connected to said slack controlelements urging the same against said endless conveyor chains in adirection to keep said chains in taut condition, said slack controlelements yielding in response to expansion and contraction of theconveyor chains upon heating and cooling thereof.

2. An apparatus for sealing cartons having closure flaps at opposedwalls thereof, said fiaps overlapping one another and having a heatsealing adhesive therebetween, said apparatus comprising a frame, a pairof endless conveyor chains extending parallel with one another alongsaid frame, said chains having vertically disposed heat exchangeelements thereof and having opposed carton-sealing runs and respectivereturn runs, each conveyor having sprockets at opposite ends thereof,said conveyor chains trained over said sprockets, respective bearingbrackets on said frame and journalling each of said sprockets, alongitudinal guide rail having opposite ends secured to the bearingbrackets of each conveyor chain and extending along said carton-sealingruns in a plane to contact the bottom of a carton advancing along saidruns, the bearing brackets of one conveyor chain being shiftabletransversely relative to the other, adjustment means connected to thelongitudinal guide rail for moving the guide rail and shiftable bearingbrackets 35 2,727,345

transversely, thereby to locate the conveyor chains-and opposed heatexchange elements at a spacing to embrace the opposed flaps of a cartonalong said carton-sealing runs, driving means connected to a sprocket ofeach conveyor chain for advancing the heat exchange elements in the samedirection along said carton-sealing runs, and heat transmitting meansmounted in fixed position relative to said guide rails and located alongsaid return runs adjacent the heat exchange elements on the sideopposite the conveyor chain thereof, said heat transmitting meanstransmitting heat to the heat exchange elements, the said adjustmentmeans regulating the pressure imposed by said heat exchange elementsupon the opposed flaps of the carton along said carton-sealing runs,said heat transmitting means shifting in unison with said longitudinalguide rails upon transverse adjustment of said rail and bracket by saidadjustment means, said heat exchange elements absorbing heat from theheat transmitting means during advancement along the return runs andtransmitting heat and pressure to the opposed flaps to seal the cartonduring advancement along the carton-sealing runs.

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